High-frequency resonator



Feb. 22, 1949. M. R. HUBBARD HIGH-FREQUENCY RESONATOR Filed March 2, 1944 706772?? Wa /9 339/554 7 54 @%W; /M

range; and; a further Patented Feb. 22, 1949 2,462,639 HIGH-FREQUENCY RESONATOR Merle Iowa R. Hubbard, Cedar Rapids, Iowa, assignor to Collins. Radio Company,

a corporation of Application March 2, 1944, Serial-No. 524,699

11 Claims.

This invention relates to a high frequency resonator, and more particularly to electrical resonator designed to operate at high and ultra high radio frequencies.

Onefeature of this invention is that it provides an-im-proved high frequency electrical resonator; another feature of this invention is that it providesan improved concentric resonator of the type. wherein the lines of force are completely controlled and kept Within an outer electrically conducting member; yet another featureof. this invention is that it provides higher inductance than heretofore possible with small concentric resonators; still another feature of this invention is. that the inductance of the resonator may be continuously varied throughout a considerable feature of this invention that it provides a concentric resonator of :the enclosed type with an improved reactance-resistance. ratio. Other features and advantages of;

this invention Will be apparent from the following-specification and the drawing, in which:

Figure l is a longitudinal. View, principally in section, of one embodiment of my invention;

Figure 2 is an end View of the same, principally brokenaway; Figure 3 is a transverse sectional view along the line 3-3 of Figure l; and Figure 4 visa. transverse sectional View along the line 4 -4. of Figure 1.

The concentric resonator which is of-this invention is sometimes termed a can type resonator in the art. It is used in tuning ultra-high frequency circuits, such a resonator sometimes acting alone as the tank circuit for ultrahigh-frequency Work. and sometimes having additional external capacity associated therewith. Can type resonators are sometimes used With single endedcircuits, and sometimes with push-pull circuits. The circuits in which they are used,

and the fundamentals of their theories and operation will not be fully described here since, if fuller information in such regard should be desired, reference may be had to such patents as Lindenblad Patent 2.245 59'? of June 7, 1941, and

Hansell Patent 2,286 408 of June 16, 1942,-for

example, and to other published patents and articles, a number of such being listed in the above mentioned patents.

The present invention comprises an outer electrically conducting member having an inner surface formed as a surface of revolution about a certain axis, as a cylinder (whence the term can) electrically conducting end plates closing the cylinder; and at least one inner member axialvvith said outer member and directly connected to, one end thereof. Such a resonator generally has two such inner members With their central. ends adjacent and a pair of parallel electrically conducting plates directly 1 the subject mounted on the adjacent ends of such inner members to provide the desired capacity. The improvements to which the present application is directed comprise: primarily, making such inner -member or members helical so as to increase'the inductance of a given size resonator and concentrate or lump such inductance in the inner member or members; secondarily, asso ciating movable members with such helical inner member. or members in such a Way that the total inductance of theresonator may be continuously varied through a substantial range; and thirdly. provldingdeep annular grooves or recesses in the inner surfaces of the end plates to improve the Qofthe resonator.

The ends of the tube, member are axially slotted for short distance tightly to receive end H and i2; and the ends of the cylinders are drawn tightly around these end plates by clamping and mounting blocks i3 and Hi. It is important that there be good mechanical and electrical contact between the ends of the cylinder andthe end plates clear around their periphery, and these parts may be soldered or welded together if desired. The mounting blocks and resonator are here shown carried by a base it providedwith end members i5 and i? serving as journal plates for the shafts of operating mechanism later to be described.

Extending into the cylinder from each end are col-responding helical inner members I8 and [9,

identical except that they are oppositely wound. These inner. helices are wound of quite rigid ribbon,- preferably wound flatwise, as for example quarter. inch brass ribbon, with about ,41 of an inch: betwen turns, in one embodiment of this resonator which has been built by me. In such embodiments there were five turns (effectively) in, the inner. members .(as illustrated here), the diameter of the helices being about inch. The outer ends of these helical inner members are rigidly mounted in and connected to the centers of theend plates ii and 12, as by soldering or welding; and their inner ends are adjacent each other and held indesired relationship by a spacer 1 member of good high frequency insulating char acteristics,as a ceramic spacer 20.

The. inner orladjacent ends ofthe inner members! and I9 have mechanically and electrically connected to them spaced parallel plates 2| and zl these, plates providing the desired capacity for certain portions of high and ultra high frequency bands. Connections are taken off from these plates through studs 23 and 24 mounted in a terminal block 25, of insulating material appropriate to high frequency work, covering a small opening through the wall of the ends of these studs serve as connecting terminals for the resonator, at least in so far as the high frequency portions of the circuit are concerned, although one of the B supply connections is sometimes made directly to the outer cylinder ID. If desired, additional external capacity, either fixed or variable, may be connected between these terminal studs. In push-pull operation, such terminals might be connected to two grids or to two plates. In using the resonator to control the frequency of an oscillator, for example, one terminal might be connected to the grid through a blocking condenser, and the other terminal connecteddirectly to the plate of the tube, B+ being connected to the shell or outer cylinder under such circumstances.

One embodiment of this invention built by me used an outer cylindrical tube 4 inches long and with two inches outer diameter, the tube being about inch thick; and five torn inner members turned on a lathe from a brass tube with /2 inch outer diameter, and about A; inch inner diameter with about inch spacing between turns. Where the inner plates provided a fixed capacity of 1.5 micro-microfarads, variation of the inductance of the inner helical members from maximum to minimum in a manner to be hereinafter described resulted in the frequency of the oscillator controlled by this resonator being varied from 187 megacycles to 317 meg-acycles; and the same resonator, with an external fixed padding capacity of 13 micro-microfarads connected across the terminal studs 23 and 24 give an oscillator frequency variation of 112 megacycles to 179 megacycles. Obviously, use of a variable external padding condenser and variation of such condenser in the same manner as variation of the inductance of the helical inner members, would result in a frequency range (in the particular model described) from 112 megacycles up to a frequency in excess of 300 megacycles, depending upon the minimum capacity of the external variable condenser.

Threaded into the outer ends of each of the helical members l8 and I9 are movable inductance varying members 26 and 21. These comprise electrically conducting rods, as of silver plated brass, with helical projecting portions of threads adapted to be received by the spaces between turns of the helical members, the proportions being such that the projecting threads are a tight fit between the turns of the inner members. Moving these members into or out of the inner members (by appropriate rotation) considerably varies the inductance of such inner members and thus of the entire resonator. That is, so much of the inner members as have the movable members threaded therein are in effect rods instead of helices; and

movement of the members 26 and 2'! from their innermost positions to withdrawn positions varies the resonator from the inductance associated with a. more conventional rod-like inner member to the more concentrated and higher value inductance associated with the helices.

In order to effect simultaneous coordinated movement of the members 26 and 27, operating means is provided external of the resonator. A shaft 28 is rigidly and coaxially connected to the member 26, this shaft being slidable and rotatable in an appropriate bushing in the end member 16,

cylinder H3. The outer I naled in the members i when associated with an oscillator resonator.

- rangement may be made 4. 30 non-rotatably mounted and gear 3| are similarly and having a gear thereon. A shaft 29 "associated with the other movable member Zl and other end member 11. tends the full length of the cylindrical member A pinion shaft 32 exthe device externally of ll), being rotatably jour- 6 and I l and projecting through one of such members, as it, in a portion adapted to have a knob or other appropriate operating means fastened thereto. This shaft car ries a pair of long pinions 34 and 35 adapted to cooperate, respectively, with the gears 3t and 3|. It will be immediately apparent from a consideration of Figure 1 that rotation of the pinion shaft 32 in one direction effects simultaneous and similar inward movement of the members 26 and 27 (these being oppositely threaded), whereas rotation in the other direction efiects similar outward movement. The provision of helical rather than conventiona1 rod-like inner members provides higher inductive reactance for a given size resonator, thus enabling the use of a reasonably small resonator for high and medium high frequencies; and the provision of the movable members 26 and 21 enables substantial variation in the inductive reactance of the resonator, so that, particularly when variation of the inductance is ganged or "coordinated with a variation of an external padding condenser, tuning ratios of 2 to 3 to 1 can be attained. Moreover, a resonator of the kind here disclosed provides very stable characteristics or in any other tuned circuit application, and has very good reset characteristics, particularly when the setting is always approached from the same direction.

As may be best seen in Figure 1, I provide the inner surfaces of the end plates l l and I2 with deep annular grooves here identified as Ha and 52a. The edges of these grooves extend clear to the inner and outer surfaces, respectively of the outer cylindrical and inner helical members; and

such grooves should have a depth at least and preferably or more of their width. Conventional end plates are merely fiat or slightly bowed discs; whereas end plates Of the kind shown, with their inner surfaces having a deep annular groove, provide much better Q in the It is my belief that this results by virtue of the ability of the flux lines to follow a more curved path at the end plates, without sharp changes of direction. Whatever the prove the reactance-resistance ratios of such a resonator, with attendant improvement in tuning sharpness, reduction in losses, etc.

While I have shown and described certain embodiments of my invention, it is to be understood that it is capable of many modifications. Changes, therefore, in the construction and arwithout departing from the spirit and scope of the invention as disclosed in the appended claims.

I claim:

1. A high frequency electrical resonator, including: an outer electrically conducting member having an inner surface formed as a surface of revolution about a certain axis; electrically conducting means closing at least one end of said member; an inner electrically conducting helical member concentric with said axis, the

ponent of the electrical resonator; and a member movable with respect to the inner helical member to short out turns thereof for varying the inductance thereof, movement into the helical member lessening the inductance thereof.

2. A high frequency electrical resonator, including: an outer electrically conducting memher having an inner surface formed as a surface for revolution about a certain axis and closed at both ends by electrically conducting means; an inner electrically conducting helical member concentric with said axis and having one end thereof directly connected to one end of said outer member, the inductance of said helical member being a component of the electrical resonator; a member movable within the inner helical member to short out turns for varying the inductance thereof; and operating means external of said outer member for effecting movement of said movable member.

3. A high frequency electrical resonator, in-

cluding: an outer electrically conducting member 3 having an inner surface formed as a surface of revolution about a certain axis and closed at both ends by electrically conducting means making contact therewith at both ends; two inner electrically conducting helical members, each being L concentric with said axis and having one end thereof directly connected to one end of said outer member, the other ends of said inner members being adjacent each other; and a pair of electrically conducting parallel plates, one being connected to one of each of the adjacent ends of said inner members.

4. Apparatus of the character claimed in claim 3, including two movable members, one being movable Within each of the inner helical members for varying the inductance thereof, and operating means external of said outer member for effecting simultaneous movement of both of said movable members.

5. A high frequency electrical resonator, in-

eluding: an outer electrically conducting memher having an inner surface formed as a surface of revolution about a certain axis and closed at both ends by electrically conducting means; two inner electrically conducting helical members, each being concentric with said axis and having one end thereof directly connected to one end of said outer member; two electrically conducting movable members, one threading into each of the inner helical members for varying the inductance thereof; and operating means external of said outer member for effecting simultaneous movement of both of said movable members.

6. A high frequency electrical resonator, including: an outer electrically conducting member having an inner surface formed as a surface of revolution about a certain axis; an electrically conducting circular end member closing an. end of said outer member; and an inner electrically conducting member concentric with said axis and having one end thereof directly connected to the center of said end member. the end member having an annular groove in the inner surface thereof intermediate said inner and outer members, the construction and arrangement being such that all changes of direction in said inner surface are substantially greater than right angles.

7. A high frequency electrical resonator, including: an outer electrically conducting member having an inner surface formed as a surface of revolution about a certain axis; an electrically conducting circular end member closing an end of said outer member; and an inner electrically conducting member concentric with said axis and having one end thereof directly connected to the center of said end member, the en memb having an annular groove in the inner surface thereof, this groove being of substantial depth and having its edges extending to said inner and outer members, the construction and arrange ment being such that all changes of direction in said inner surface are substantially greater than right angles.

8. A high frequency electrical resonator, including: an outer electrically conducting member having an inner surface formed as a surface of revolution about a certain axis; an electrically conducting circular end member closing an end of said outer member; and an inner electrically conducting helical member concentric with said axis and having one end thereof directly connected to the center of said end member, the end member having an annular groove in the inner surface thereof intermediate said inner and outer members, said groove having a depth at least equal to one-third its Width, the construction and arrangement being such that all changes of direction in said inner surface are substantially greater than right angles.

9. A high frequency electrical resonator, including: an outer electrically conducting member having an inner surface formed as a surface of revolution about a certain axis; electrically conducting means closing at least one end of said member; an inner electrically conducting helical member concentric with said axis; and an electrically conducting movable member threading into the inner helical member for varying the inductance thereof.

10. A high frequency electrical resonator, including: an outer electrically conducting member having an inner surface formed as a surface of revolution about a certain axis and closed at both ends by electrically conducting means; two inner electrically conducting helical members, each being concentric with said axis and one of said helical members having one end thereof directly connected to one end of said outer member and the other of said helical members having one end thereof directly connected to the other end of said outer member, the inductance of said helical members being a component of the electrical resonator; and means for varying the effective turns of said hel cal member whereby the inductance of said inner members is varied.

11. Anparatus of the character claimed in claim 10 wherein said last-mentioned means includes two movable members, one being movable Within each of the inner helical members for varying the inductance thereof and wherein there is operating means external of said outer member for effect ng simultaneous movement of both of said movable members.

MERLE R. HUBBARD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,028,596 Franklin et a1 Jan. 21, 1936 2,115.882 Rust et a1 May 3, 1938 2169.352 Buschbeck Aug. 15, 1939 2,236,004 MacLean Mar. 25, 1941 2,337,219 Zottu Dec. 21, 1943 FOREIGN PATENTS Number Country Date 432,040 Great Britain July 19, 1935 

